WO2012118120A1 - Transmission for automatic two-wheeled vehicle - Google Patents

Abstract

A transmission for a two-wheeled vehicle, comprising: an input shaft that transmits motive force from a crank shaft; an output shaft; a plurality of gear pairs having a gear that rotates in conjunction with the input shaft and a gear that meshes with said gear and is freely rotatable relative to the output shaft, and each having different gear ratios; a plurality of dog clutches that make each of the plurality of gear pairs intermittently rotate freely relative to or in conjunction with the output shaft; a plurality of shift forks (7) that intermittently transmit motive force to each of the plurality of dog clutches; and a shift cam that is capable of moving the plurality of shift forks and selectively transmitting motive force to one of the plurality of gear pairs.

Description

Motorcycle transmission

The present invention relates to a transmission for a motorcycle.

A transmission (so-called transmission) in a vehicle transmits power between a prime mover such as an engine and an output shaft such as an axle, and converts the rotational speed, torque, and the like of the transmitted power. For example, a dog clutch type (also referred to as “always meshing type”) manual transmission is known as a transmission that has been widely applied as a manual transmission for motorcycles.

A conventional transmission of this type includes, for example, an input shaft that receives power from an engine crankshaft, an output shaft that transmits power to an axle via, for example, a drive chain, a gear on the input shaft side, and an output shaft side gear. And a plurality of gear pairs having different gear ratios.

The gear pair includes a movable gear that is coupled to the input shaft so as to rotate together and a movable fitting gear that is always meshed with the movable gear and that is rotatable on the output shaft. There are a pair of gears including a combination gear and a movable gear that is always meshed with the loose fitting gear and is coupled to the output shaft in a rotationally integrated manner. The movable gear rotates integrally with the shaft by a groove (spline) extending in the rotation axis direction of the input shaft or the output shaft and can slide in the rotation axis direction at the same time.

In addition, the transmission includes a plurality of dog clutches that can be freely rotated or integrated by intermittently engaging and disengaging idle coupling gears for each gear pair, a plurality of shift forks that are intermittently engaged for each dog clutch, and a plurality of shift forks. A shift cam that moves to selectively transmit power to any one of the plurality of gear pairs.

The movable gear is a so-called shifter gear and is integrally formed with the dog selector.

A shift cam is provided close to both sides so that the shift fork extending to the input shaft or the output shaft does not become excessively long at the upper rear side of the input shaft.

In the transmission, any one of the loosely fitted gears and the shaft is rotated and integrated by a shift fork and a dog clutch, and the gear ratio is changed by selectively allowing a plurality of gear pairs to transmit power (see, for example, Patent Document 1). .)

Further, in the conventional transmission, the side of the crankcase extends in the vertical direction of the vehicle in order to connect the shift lever and the shift cam for the convenience of arranging the shift cam obliquely behind and above the input shaft, that is, above the crankcase. A relatively long link (so-called shift link rod) is provided (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 10-77861 JP-A-9-123972

The above-described conventional transmission needs to include a shift fork extending to the input shaft side dog clutch and a shift fork extending to the output shaft side dog clutch because the loosely fitted gears and the dog clutch are dispersed on the input shaft and the output shaft, respectively. There is. This necessitates that the shift cam be arranged close to both the input shaft and the output shaft, and the degree of freedom of arrangement of the shift cam is significantly impaired.

More specifically, in the case of the transmission described in Patent Document 1, the crankshaft that is closer to the front of the crankcase in a side view of the engine, the input shaft that is obliquely above and behind the crankshaft, and the obliquely rearward and lower portion of the input shaft Because the output shaft is located in a triangular shape, the shift cam is close to both the input shaft and the output shaft, and does not interfere with the power transmission between the crankshaft and the input shaft. It is preferably located behind the plane passing through the axis of rotation of the shaft (more specifically, obliquely behind and above the input shaft), and the degree of freedom in arrangement is extremely low.

On the other hand, since the engine transmits power from the output shaft to the drive wheels via a transmission mechanism such as a drive chain or drive belt, it is necessary to dispose a bracket that suspends the engine on the vehicle body so as not to interfere with these transmission mechanisms. Arise. For example, in the case of the transmission described in Patent Document 1, one of the brackets is arranged to avoid the rear side of the output shaft and prevent interference with the transmission mechanism.

By the way, when the transmission mechanism transmits power to the drive wheel, the engine receives a tensile load directed rearward on the output shaft. As the distance between the output shaft and the bracket is longer (that is, the moment arm is longer), the tensile load acting on the output shaft may cause a larger bending stress in the crankcase and hinder the smooth operation of the transmission. . However, in the case of the transmission described in Patent Document 1, one of the brackets in the vicinity of the output shaft not only avoids interference with the transmission mechanism, but further away from the output shaft by avoiding the shift cam and the shift fork. Therefore, the bending stress generated in the crankcase due to the tensile load acting on the output shaft is promoted, and the smooth operation of the transmission is hindered.

Also, the fact that the shift cam must be in close proximity to both the input shaft and the output shaft significantly moves the shift cam and the vehicle footrest in the vertical direction of the vehicle. For example, in the case of the transmission described in Patent Document 2, a motorcycle has a relatively long link (so-called shift gear) that extends in the vertical direction of the vehicle in order to connect a shift lever and a shift cam. Link rod) is required. In order for the rider to place his / her foot on the footrest, in order to avoid interference between the rider's leg and the link, the extending direction of the link and the rotation center position of the shift lever are restricted. This prevents the shift lever from moving around the center of rotation even if the footrest position is adjusted appropriately according to the rider's physique (especially the length of the legs), making the operability and operational feel of the shift lever uncomfortable. Will occur.

Therefore, in view of the above-described conventional technology, an object of the present invention is to provide a motorcycle transmission having a very high degree of freedom in the arrangement of a shift cam with respect to an input shaft and an output shaft.

In order to solve the above problems, a transmission for a motorcycle according to the present invention includes a first power transmission shaft that is one of an input shaft and an output shaft that transmits power from a crankshaft, the input shaft, and the output. A second power transmission shaft which is the other of the shafts, one gear which is rotationally integrated with the first power transmission shaft, and the other gear which meshes with the one gear and is rotatable with respect to the second power transmission shaft. A plurality of gear pairs each having a different gear ratio; a plurality of dog clutches that rotate or integrate the other gear intermittently to the second power transmission shaft for each of the plurality of gear pairs; A plurality of shift forks that perform intermittent transmission of power for each dog clutch; and a shift cam that moves the plurality of shift forks to selectively transmit one of the plurality of gear pairs. It is characterized in.

According to the motorcycle transmission of the present invention having the above characteristics, it is possible to set an extremely high degree of freedom in arranging the shift cam with respect to the input shaft and the output shaft.

Further detailed configuration and characteristics of the present invention will be further clarified from the description of the following embodiments described with reference to the accompanying drawings.

1 is a left side view of a motorcycle to which a transmission according to an embodiment of the present invention is applied. 1 is a left side view of a motorcycle engine to which a transmission according to an embodiment of the present invention is applied. 1 is a right side view of an engine of a motorcycle to which a transmission according to an embodiment of the present invention is applied. The right view which shows the transmission which concerns on embodiment of this invention. 1 is a sectional view showing a transmission of a motorcycle according to an embodiment of the present invention. The expansion exploded perspective view showing the dog clutch and gear of the transmission concerning the embodiment of the present invention. The perspective view which shows the engine which applies the transmission which concerns on embodiment of this invention. The perspective view which shows the transmission which concerns on embodiment of this invention. 1 is a left side view showing a shift lever of a motorcycle to which a transmission according to an embodiment of the present invention is applied. 1 is a cross-sectional view showing a shift lever of a motorcycle to which a transmission according to an embodiment of the present invention is applied.

Embodiments of a motorcycle transmission according to the present invention will be described with reference to the accompanying drawings.

In the present embodiment, front and rear, top and bottom, and left and right expressions are based on the rider who rides the motorcycle 1.

FIG. 1 is a left side view showing a motorcycle to which a transmission according to an embodiment of the present invention is applied.

In FIG. 1, a motorcycle 1 includes a body frame 2, a front wheel 5 positioned in front of the body frame 2, a steering mechanism 6 that rotatably supports the front wheel 5 on the body frame 2, and a rear side of the body frame 2. A rear wheel 7 that is positioned, a swing arm 8 that extends rearwardly of the body frame 2 and rotatably supports the rear wheel 7, and an engine 10 that is an internal combustion engine positioned in the lower center of the vehicle are provided.

The vehicle body frame 2 is, for example, a twin tube type, and a pair of left and right main frames 12 that extend in a pair in the left-right direction immediately after the head pipe 11 positioned at the front upper end and extend downward and obliquely downward in parallel to each other. A pair of left and right center frames 13 connected to the rear end portion of the main frame 12 and extending substantially upward and downward, and a pair of left and right seat rails 15 extending rearward from the rear upper end portion of the center frame 13 are provided.

The main frame 12 also serves as a tank rail, supports the fuel tank 16 positioned above the main frame 12, and suspends the engine 10 below the fuel tank 16. The seat rail 15 supports a rider seat 17 located in the upper front half and a pillion seat 18 located in the upper rear half. The main frame 12 is positioned substantially at the center lower part of the left and right center frames 13 and is pivotally supported by the swing arm 8 so as to be swingable in the vertical direction. And a shift lever 22 extending from the footrest 21 on the left side of the vehicle.

The steering mechanism 6 includes a pair of left and right front forks 23 that support a front wheel 5 so that the front wheel 5 can be pivotally mounted with a suspension mechanism (not shown), and a handle bar 25 that is positioned at the upper end of the front fork 23. The rider steers the front wheel 5 left and right by the handle bar 25.

The engine 10 is connected to an exhaust pipe 26 that extends rearward of the vehicle and exhausts the exhaust gas of the engine 10. The rear end of the exhaust pipe 26 is connected to the exhaust muffler 27.

The rear wheel 7 includes a driven sprocket 28.

The motorcycle 1 also includes a drive chain 29 that is wound around a driven sprocket 28 and transmits power from the engine 10 to the rear wheel 7, and a streamlined cowling 30 that covers the front of the vehicle. The cowling 30 reduces air resistance during traveling and protects the rider from traveling wind pressure.

Next, the engine 10 according to the present embodiment will be described in detail.

2 and 3 are a left side view and a right side view showing an engine to which the transmission according to the embodiment of the present invention is applied.

As shown in FIGS. 2 and 3, the engine 10 according to the present embodiment is a four-cycle multi-cylinder engine, for example, a four-cycle in-line four-cylinder engine, and includes a crankcase 31, a cylinder block 32, a cylinder head 33, A head cover 35, an oil pan 36, and a clutch mechanism 37 are provided.

The crankcase 31 can be divided into two vertically by a dividing surface 31a, and includes an upper crankcase 38 as a first case half and a lower crankcase 39 as a second case half. The crankcase 31 includes a plurality of brackets 40 that suspend the engine 10 from the vehicle body frame 2.

As shown in the figure, the cylinder block 32 is located at the upper part of the upper crankcase 38 and is inclined slightly forward from the upright position. The cylinder block 32 has a cylinder bore (not shown) that houses a piston (not shown) so as to be slidable in a substantially vertical direction.

The cylinder head 33 closes the cylinder bore and partitions a combustion chamber (not shown) with the piston. The piston reciprocates by the combustion of the air-fuel mixture that occurs periodically in the combustion chamber.

The oil pan 36 is attached to the lower part of the lower crankcase 39.

The clutch mechanism 37 is a dry clutch. The clutch cover 41 is assembled to the side wall of the crankcase 31 and partially covers the clutch mechanism 37.

FIG. 4 is a right side view showing the transmission according to the embodiment of the present invention. 4 is a view showing the engine 10 with the clutch cover 41 and the clutch mechanism 37 removed.

2 to 4, the engine 10 includes a crankshaft 42 and a transmission 43 in the crankcase 31.

First, the crankshaft 42 is substantially in the center in a side view of the engine 10, and is located below the cylinder block 32, more specifically, in the vicinity of the position where the split surface 31a of the crankcase 31 and the extension line of the cylinder center line intersect. The rotation axis of the crankshaft 42 faces the width direction of the engine 10.

Next, the transmission 43 is a unit-type transmission that is detachable integrally inside and outside the transmission chamber 45 that the upper crankcase 38 and the lower crankcase 39 cooperate to partition into the crankcase 31. The transmission 43 includes an input shaft 46, an output shaft 47, a shift mechanism 48, and a mission cover 49 that rotatably supports the input shaft 46 and the output shaft 47.

The crankshaft 42, the input shaft 46, and the output shaft 47 have rotation axes that are parallel to each other. The crankshaft 42 rotatably holds a primary drive gear 51 that transmits power to the input shaft 46.

The input shaft 46 is positioned obliquely above and behind the crankshaft 42 on the dividing surface 31a and is connected to the clutch mechanism 37. The input shaft 46 rotatably supports a primary driven gear 52 that meshes with the primary drive gear 51.

The output shaft 47 is located below the input shaft 46 (slightly behind and below). The output shaft 47 protrudes outward on the left side of the crankcase 31 and is coupled to the drive sprocket 53. The drive sprocket 53 is wound around the drive chain 29 and transmits power to the rear wheel 7.

The shift mechanism 48 is located below the output shaft 47. The shift mechanism 48 includes a shift cam 55 and a fork shaft 56. The shift cam 55 is below the output shaft 47. The fork shaft 56 is located behind the shift cam 55 and in front of the rearmost end of the outer periphery of the clutch mechanism 37.

The input shaft 46, the output shaft 47, and the shift cam 55 are arranged in a straight line in order from the top, and the respective rotation axes are in substantially the same plane.

FIG. 5 is a cross-sectional view showing the transmission of the motorcycle according to the embodiment of the present invention cut along line VV in FIG.

As shown in FIG. 5, the clutch mechanism 37 of the engine 10 according to the present embodiment includes a clutch body 63 that holds the primary driven gear 52 in a rotationally integrated manner. The clutch mechanism 37 intermittently rotates or integrates the primary driven gear 52 with the input shaft 46 to cut off or transmit power between the crankshaft 42 and the input shaft 46.

The transmission 43 is a so-called dog clutch type manual transmission. The transmission 43 includes an input shaft 46 as a first power transmission shaft for transmitting power from the crankshaft 42, an output shaft 47 as a second power transmission shaft, and a gear 65 (one side) coupled to the input shaft 46 so as to rotate together. ) And a gear 66 (the other gear) that meshes with the gear 65 and is freely loosely fitted to the output shaft 47, each having a plurality of gear pairs 67 having different gear ratios, and a gear for each of the plurality of gear pairs 67. The input shaft 46 in cooperation with the crankcase 31, the plurality of dog clutches 69 that are connected to the output shaft 47 to be freely rotated or integrated, the plurality of shift forks 71 that are intermittently connected to each of the plurality of dog clutches 69. And a mission cover 49 that pivotally supports the output shaft 47.

The one end portion (here, the right end portion) of the input shaft 46 holds the primary driven gear 52 and the clutch mechanism 37. The input shaft 46 has a spline 46a on the outer periphery.

The output shaft 47 receives the power of the engine 10 from the input shaft 46 and outputs it outside the transmission 43. The output shaft 47 has a spline 47a on the outer periphery. Note that the spline 47a does not exist in the portion where the gear 66 is loosely fitted.

The gear 65 is a fixed gear that is joined to the input shaft 46 in a rotationally integrated manner. The plurality of gears 65 include a counter shaft low gear 65a, a counter shaft second gear 65b, a counter shaft third gear 65c, a counter shaft force gear 65d, a counter shaft top gear 65e, and a counter shaft overtop gear 65f (hereinafter simply referred to as “gear 65a”). , "Gear 65b", "gear 65c", "gear 65d", "gear 65e" and "gear 65f").

The gear 66 is a loosely fitted (freely fitted) gear that is freely loosely fitted to the output shaft 47. The gear 66 includes a drive shaft low gear 66a, a drive shaft second gear 66b, a drive shaft third gear 66c, a drive shaft force gear 66d, a drive shaft top gear 66e, and a drive shaft overtop gear 66f (hereinafter simply referred to as “gear 66a”, “gear”). 66b "," gear 66c "," gear 66d "," gear 66e "and" gear 66f ").

Gears 65 and 66 are located between a pair of left and right bearings 73 that support the input shaft 46 and the output shaft 47, respectively.

The transmission 43 has a gear 65a and a gear 66a, a gear 65b and a gear 66b, a gear 65c and a gear 66c, a gear 65d and a gear 66d, a gear 65e and a gear 66e, a gear 65f and a gear 66f, and a gear 65f and a gear 66f. This is a six-speed type that can shift up to

Hereinafter, the gears 65 and 66 will be described in detail.

The gear 65 b is the rightmost gear and is an integral gear with the input shaft 46. The gear 65a is the leftmost, the gear 65c is the second from the left, the gear 65d is the second from the right, the gear 65e is the third from the left, and the gear 65f is the third from the right. The gears 65 b, 65 c, 65 d, 65 e, and 65 f are coupled to the input shaft 46 by a spline 46 a of the input shaft 46 so as to rotate together.

On the other hand, the gear 66a is the leftmost, the gear 66b is the rightmost, the gear 66c is the second from the left, the gear 66d is the second from the right, the gear 66e is the third from the left, and the gear 66f is the third from the right. It is in. The slide bearing 75 rotatably supports the gear 66 on the output shaft 47.

The transmission 43 includes a plurality of sleeve-like spacers 76 and 77 that are sandwiched between adjacent gear pairs 67 and restrict movement of the plurality of gear pairs in the rotation axis direction.

The spacer 76 is sandwiched between the gears 65 and restrains the separation distance between the adjacent gears 65. The spacer 76 has a through hole into which the input shaft 46 is inserted. The spacer 76 is fitted into the spline 46 a and is rotated and integrated with the input shaft 46.

The spacer 77 is sandwiched between the gears 66 and restrains the separation distance between the adjacent gears 66. The spacer 77 has a through hole into which the output shaft 47 is inserted. The spacer 77 is fitted into the spline 47 a and is rotated and integrated with the output shaft 47. The spacer 77 has splines 77a on the inner and outer peripheral portions.

The dog clutch 69 is a dog clutch 69a that makes the gear 66a or the gear 66c intermittently connected to the output shaft 47 to be rotatable or is integrated with the output shaft 47, and a dog clutch 69 that makes the gear 66b or gear 66d intermittently connected to the output shaft 47 to be rotatable or integrated with the rotation. 69 b, the gear 66 e or the gear 66 f is applied to the dog clutch 69 c which is intermittently rotated or integrated with the output shaft 47. The dog clutch 69 also includes a dog selector 78 positioned between the gears 66 adjacent to each other. The dog selector 78 is coupled to the spacer 77 so as to be fitted to the spline 77 a and to be slidable in the direction of the rotation axis of the output shaft 47. The dog selector 78 has a shift fork fitting groove 79 into which the shift fork 71 is inserted.

The dog selector 78 is applied to a dog selector 78a positioned between the gear 66a and the gear 66c, a dog selector 78b positioned between the gear 66b and the gear 66d, and a dog selector 78c positioned between the gear 66e and the gear 66d.

FIG. 6 is an exploded perspective view showing the dog clutch and gear of the transmission according to the embodiment of the present invention in an enlarged manner.

As shown in FIG. 6, the dog clutch 69 includes a plurality of convex portions 81 and concave portions 82 that can be coupled to and detached from the dog selector 78 and the gear 66. The convex portion 81 and the concave portion 82 are located at substantially equal intervals in the circumferential direction of the dog selector 78 and the gear 66.

In FIG. 6, the teeth of the gear 66 are omitted.

FIG. 7 is a perspective view showing an engine to which the transmission according to the embodiment of the present invention is applied, and shows the transmission 43 taken out from the mission chamber 45.

FIG. 8 is a perspective view showing the transmission according to the embodiment of the present invention, and is a diagram of the transmission 43 shown without the mission cover 49. 7 and 8 show gear gears omitted.

As shown in FIGS. 7 and 8, the shift mechanism 48 of the transmission 43 according to the present embodiment is capable of sliding a plurality of shift forks 71 and the shift forks 71 in a direction substantially parallel to the rotation axis of the output shaft 47. A fork shaft 56 that supports the shaft, and a shift cam 55 that moves the plurality of shift forks 71 to selectively transmit power to any one of the plurality of gear pairs 67 are provided.

The shift fork 71 enters slightly forward from the envelope passing through the rearmost end of the gear pair 67 and extends from the fork shaft 56 to the dog selector 78.

The shift cam 55 has a shift groove (not shown) that is paired with each shift fork 71 on the outer periphery. The shift cam 55 rotates by the operation of the shift lever 22, slides the shift fork 71 along the shift groove, and selectively connects the dog clutch 69 and the gear 66 to drive power between the input shaft 46 and the output shaft 47. Enable transmission.

On the other hand, the crankcase 31 includes a bracket 40a located on the left rear side of the transmission 43, a bracket 40b located on the right rear side of the transmission 43, and a bracket 40c located on the lower side of the transmission 43.

The brackets 40a and 40b and the bracket 40c suspend the engine 10 on the vehicle body frame 2 in cooperation with the other brackets 40 of the crankcase 31. In particular, the bracket 40 a is located closest to the drive sprocket 53 and most strongly supports the reaction force of the tensile load acting on the output shaft 47 from the drive chain 29.

The bracket 40a is located at a position very close to the drive chain 29 and the output shaft 47 as shown in FIGS. In the transmission 43, the shift mechanism 48 is positioned below the output shaft 47, and by disposing no shaft or the like behind the output shaft 47, the wall surface of the crankcase 31 can be as close to the output shaft 47 as possible. The bracket 40a is brought close to the drive chain 29 and the output shaft 47.

FIG. 9 is a left side view showing a shift lever of a motorcycle to which the transmission according to the embodiment of the present invention is applied, and FIG. 10 applies the transmission cut along line XX in FIG. It is sectional drawing which shows the shift lever of a motorcycle.

As shown in FIGS. 9 and 10, the shift lever 22 of the motorcycle 1 according to this embodiment has a rotation axis that is coaxial with the footrest 21 and has an arm length that can be swung on the toe T of the rider.

On the other hand, the shift cam 55 of the transmission 43 includes a shift link arm 85. Since the shift cam 55 is located at the lowermost part of the transmission 43, the shift link arm 85 is at a very low position even when viewed from the engine 10 as a whole.

The shift lever 22 and the shift link arm 85 are connected by a shift link rod 86 that is positioned below the footrest 21 and extends. The shift link rod 86 constitutes a link mechanism together with the shift link arm 85 and the arm portion 87 suspended from the rotation base portion of the shift lever 22, and transmits the swing of the shift lever 22 to the shift cam 55 to rotate the shift cam 55, thereby transmitting the transmission. 43 shifts are urged.

When changing or adjusting the position of the footrest 21 according to the rider's physique, the shift lever 22 moves together with the footrest 21, and changing the distance between the shift lever 22 and the shift link arm 85 adjusts the length of the shift link rod 86. And respond. Such a correspondence is possible even if the rotation axis of the shift lever 22 moves, because the shift link rod 86 is always positioned below the rider's foot. This is because there is no need to take into account interference.

In the transmission 43, the combination of the input shaft 46 and the output shaft 47, and the gear 65 and the gear 66 can be changed as appropriate. Specifically, the transmission 43 has a gear 65 (one gear) that is integrally rotated with the output shaft 47 and a gear 66 (the other gear) that meshes with the gear 65 and is freely rotatable with respect to the input shaft 46. A plurality of gear pairs 67 having different from each other may be provided. In this case, the output shaft 47 is a first power transmission shaft, and the input shaft 46 is a second power transmission shaft.

According to the transmission 43 of the motorcycle 1 according to this embodiment described above, the following effects and advantages are achieved.

That is, all of the shift forks 71 of the output shaft 47 (or the input shaft 46) are arranged by concentrating all of the gears 66 and the dog clutches 69, which are idle fitting gears, on the output shaft 47 (or the input shaft 46). Can be placed around. This enables not only the shift fork 71 but also the entire shift mechanism 48 including the shift cam 55 to be arranged around the output shaft 47 (or the input shaft 46), and the degree of freedom in the arrangement of the shift mechanism 48 is dramatically increased. improves. Specifically, the transmission 43 allows the shift mechanism 48 to be moved to an arbitrary position around the output shaft 47 (or the input shaft 46) within a range in which interference with the crankshaft 42 and the input shaft 46 (or the output shaft 47) can be avoided. Can be placed in phase.

In addition, the transmission 43 of the motorcycle 1 according to the present embodiment improves the degree of freedom of the arrangement of the shift mechanism 48, thereby arranging the shift mechanism 48 below the output shaft 47, etc. The side wall surface and the bracket 40a can be arranged as close to the output shaft 47 as possible. As a result, the transmission 43 suppresses bending stress generated in the crankcase 31 by shortening the moment arm for the tensile load acting on the output shaft 47 from the transmission mechanism such as the drive chain 29 and the drive belt as much as possible. Smooth operation can be secured.

Further, the transmission 43 of the motorcycle 1 according to the present embodiment improves the degree of freedom of the arrangement of the shift mechanism 48, thereby disposing the shift link rod 86 by arranging the shift mechanism 48 below the output shaft 47. Arranged below the footrest 21, the possibility of interference between the rider's legs and the shift link rod 86 can be eliminated. This makes it possible to arrange the footrest 21 and the shift lever 22 without being restricted by the constraint of avoiding interference between the rider's leg and the shift link rod 86. Specifically, when changing or adjusting the position of the footrest 21 according to the rider's physique, the transmission 43 enables the shift lever 22 to move together with the footrest 21, thereby improving the operability and operational feeling of the shift lever. improves.

Furthermore, the transmission 43 of the motorcycle 1 according to the present embodiment has the input shaft 46, the output shaft 47, and the shift mechanism 48 arranged in order from the top, thereby shortening the longitudinal length of the engine 10, and the motorcycle 1 as a whole. Can contribute to downsizing.

Furthermore, the transmission 43 of the motorcycle 1 according to the present embodiment arranges the input shaft 46, the output shaft 47, and the shift mechanism 48 in this order from the top, thereby transmitting the transmission to the input shaft 46, the output shaft 47, and the shift mechanism 48. Lubricating oil dripping in the chamber 45 can be reliably supplied and lubricated.

By the way, since a conventional transmission includes a so-called shifter gear in which a movable gear and a dog selector are integrally formed, when changing a gear pair for transmitting power (that is, shifting), the shifter gear is slid in the direction of the rotation axis. The loose fitting gear adjacent to the shifter gear and the rotating shaft are rotated and integrated. The force required to slide the shifter gear is a rotational load of the shift cam, that is, a load of the operating force of the shift lever because the movable gear is always meshed with the loosely fitted gear.

Conventional transmissions use a shift fork to position the shifter gear in the rotational axis direction. Therefore, if a large load is applied to the input shaft or output shaft and a load is applied to the shifter gear, the sliding surface between the shift fork and the shifter gear is applied. Wear may occur.

However, in the transmission 43 of the motorcycle 1 according to the present embodiment, all of the gear 66 and the dog clutch 69 that are idle fitting gears are concentrated on the output shaft 47 (or the input shaft 46). The gears 65 and 66 are separate parts, and the meshing of the gear pair 67 does not affect the sliding of the dog selector 78, the rotational load of the shift cam 55, and the load of the operating force of the shift lever 22.

Further, in the transmission 43 of the motorcycle 1 according to the present embodiment, all of the gear 66 and the dog clutch 69 which are idle fitting gears are concentrated on the output shaft 47 (or the input shaft 46), and the dog selector 78 and the gear are arranged. By separately setting 65 and 66 as separate parts, it is possible to perform gear shifting without sliding the gears 65 and 66. That is, the shift fork 71 can localize the dog selector 78 without receiving a load from the gears 65 and 66, and the force applied to the sliding surface between the shift fork 71 and the dog selector 78 is applied to the conventional transmission. Compared with this, the wear of the shift fork 71 and the dog selector 78 is suppressed.

Therefore, according to the transmission 43 of the motorcycle 1 according to the present embodiment, the degree of freedom in arranging the shift cam 55 with respect to the input shaft 46 and the output shaft 47 can be increased.

The present invention is not limited to the above-described embodiments, and other changes and modifications within the scope of the claims of the present invention are also within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Motorcycle 2 Body frame 5 Front wheel 6 Steering mechanism 7 Rear wheel 8 Swing arm 10 Engine 11 Head pipe 12 Main frame 13 Center frame 15 Seat rail 16 Fuel tank 17 Rider seat 18 Pillion seat 19 Pivot shaft 21 Footrest 22 Shift lever 23 Front Fork 25 Handle bar 26 Exhaust pipe 27 Exhaust muffler 28 Driven sprocket 29 Drive chain 30 Cowling 31 Crankcase 32 Cylinder block 33 Cylinder head 35 Head cover 36 Oil pan 37 Clutch mechanism 38 Upper crankcase 39 Lower crankcase 40, 40a, 40b, 40c Bracket 41 Clutch cover 42 Crankshaft 43 Transmission 45 Transmission chamber 46 Input shaft 46 Spline 47 Output shaft 47a Spline 48 Shift mechanism 49 Mission cover 51 Primary drive gear 52 Primary driven gear 53 Drive sprocket 55 Shift cam 56 Fork shaft 63 Clutch body 65, 66 Gear 67 Gear pair 69, 69a, 69b, 69c Dog clutch 71 Shift fork 73 Bearing 75 Slide bearing 76, 77 Spacer 77a Spline 78, 78a, 78b, 78c Dog selector 79 Shift fork fitting groove 81 Protruding portion 82 Recessing portion 85 Shift link arm 86 Shift link rod 87 Arm portion

Claims (6)

A first power transmission shaft that is one of an input shaft and an output shaft for transmitting power from the crankshaft;
A second power transmission shaft which is the other of the input shaft and the output shaft;
A plurality of gear pairs having one gear rotatingly integrated with the first power transmission shaft and the other gear meshing with the one gear and rotatable with the second power transmission shaft, each having a different gear ratio;
A plurality of dog clutches that intermittently rotate or integrate the other gear with the second power transmission shaft for each of the plurality of gear pairs;
A plurality of shift forks for performing intermittent transmission of power for each of the plurality of dog clutches;
A transmission for a motorcycle, comprising: a shift cam that moves the plurality of shift forks to selectively transmit power to any one of the plurality of gear pairs. 2. The motorcycle transmission according to claim 1, further comprising a spacer that is sandwiched between the adjacent gear pairs and restricts movement of the plurality of gear pairs in a rotation axis direction. The transmission for a motorcycle according to claim 1, wherein the first power transmission shaft, the second power transmission shaft, and the rotation axis of the shift cam are in substantially the same plane. The motorcycle transmission according to claim 1, wherein the shift cam is located below the first power transmission shaft. The motorcycle transmission according to claim 1, wherein the shift cam is located below the second power transmission shaft. 2. The motorcycle transmission according to claim 1, wherein the shift cam is located below the crankshaft.

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